Rain and fog
Rain does two things at once: it lengthens your stopping distance and it shortens how far you can see. Slow down and increase the gap to the vehicle in front.
In fog or mist, increase that gap further. Fog is the condition in which vehicles must keep an unusually wide distance from each other, because the vehicle ahead becomes visible far too late.
Use dipped headlights, not full beam - full beam reflects off fog and blinds you.
If you cannot see through the screen in rain, switch on the wipers before you are struggling. Standing water pulls at the steering, so hold the wheel firmly and avoid sudden braking.